Water hardness has numerous deleterious effects in various systems. For example, when hard water alone, or in conjunction with cleaning compositions, contacts a surface, it can cause precipitation of hard water scale on the contacted surface. Hard water is also known to reduce the efficacy of detergents. In general, hard water refers to water having a total level of calcium and magnesium ions in excess of about 100 ppm expressed in units of ppm calcium carbonate. Often, the molar ratio of calcium to magnesium in hard water is about 2:1 or about 3:1. Although most locations have hard water, water hardness tends to vary from one location to another.
Water hardness has been addressed in a number of ways. Most cleaning products contain one or more ingredients whose presence is intended to offset the effects of hard water. Examples include phosphorus-containing and especially phosphate-containing acids (or more commonly salts thereof, including sodium or potassium salts) such as sodium tripolyphosphate (STPP) and sodium etidronate. Other such ingredients include threshold agents, such as aminocarboxylates (for example, ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), nitrilotriacetic acid (NTA) and their salts) and polycarboxylates (for example, polyacrylates, polymethacrylates and olefin/maleic acid copolymers). However, there may be difficulties in including such ingredients in cleaning products, as several of these ingredients have been banned in various states or subjected to regulatory amount limitations due to environmental concerns (e.g., eutrophication and biodegradability) or other factors, and some are very costly.
Another method currently used to soften water is via ion exchange, e.g., by adding sodium to the water to exchange the calcium and magnesium ions in the water with sodium associated with a resin bed (or the like) in a water softening unit. The calcium and magnesium adhere to a resin in the softener. When the resin becomes saturated it is necessary to regenerate it using large amounts of sodium chloride dissolved in water. The sodium displaces the calcium and magnesium, which is flushed out in a briny solution along with the chloride from the added sodium chloride. When water softeners regenerate they produce a waste stream that contains significant amounts of chloride, creating a burden on the system, e.g., sewer system, in which they are disposed of, including a multitude of downstream water re-use applications like potable water usages and agriculture.
The use of an insoluble magnesium compound, such as a magnesium oxide bed, is used to prevent or reduce scaling (e.g. hard water scaling, silica scaling). Use of magnesium is believed to cause calcium carbonate in hard water to crystallize into a non-scaling form rather than crystals of calcite causing hard water scale is a further method. However, certain performance difficulties often impede its ability to control water hardness. In some instances, the magnesium oxide bed is limited by its slow “cementing.” “Cementing” is a phenomenon in which the discrete particles of magnesium oxide become tightly bound together, such as through the bridging of the magnesium oxide granules by calcium carbonate. This reduces the efficiency of the magnesium oxide, creating a non-fluidizable bed that is no longer free-flowing. The cementing effect makes it very difficult to remove the granules from the bed, cartridge or other types of containers, causing deleterious effects to the system for treating hard water as it eventually forms into an intractable block during the course of use and limiting commercial viability.
A further method of counteracting water hardness is to use chelating agents or sequestrants which are intended to be mixed with hard water in an amount sufficient to handle the hardness. However, in many instances the water hardness exceeds the capacity of the chelant or threshold agent added to the composition.
In yet a further method of counteracting water hardness, a cation exchange resin with a divalent ion exchange capacity fully exhausted can be used to form and shed a threshold agent in situ into a system. However control over the quantity of threshold agent shed can be difficult.
Accordingly, it is an objective of the claimed invention to develop a method for reducing hard water scaling superior to the use of water treatment systems using exhausted cation exchange resins or magnesium oxide beds, cartridges or other types of containers alone. A further object of the invention is a system for eliminating hard water scaling for use in various cleaning applications.
A further object of the invention is a system and methods for eliminating the cementing of magnesium oxide beds, cartridges or other types of containers.